Transgenic construct used in an enhancer blocking assay, containing w and y reporters, oriented divergently. Contains two Ecol\lexA binding regions (comprised of six Ecol\lexA binding sites); one binding region is inserted between the y wing and body enhancers and y promoter, and the other between the w eye enhancer and w promoter. A gypsy element is inserted at the 3' end of the w gene to prevent position effects.